Think back to your hide and seek days. You slowed your breathing and stayed as still as you could for as long as you could; fear and excitement coursed through your body as “the seeker” walked past you. Well, a new study by researchers at the University of Western Australia found that some baby sharks do the same thing to hide from predators.

The study, titled Survival of the Stillest: Predator Avoidance in Shark Embryos, looks specifically at the brownbranded bamboo shark (Chiloscyllium punctatum) whose embryos develop in an egg case. This means that baby bamboo sharks develop independently, separate from their mother. As they develop externally, they need a way to avoid predation before they hatch. Sharks and other animals have been shown to use electroreception (detection of electric field) to detect predators and prey alike, but this particular study sheds light on how this particular species of shark embryo responds to predators while still in the egg case.

Sharks use an array of pores on the surface of their skin called Ampullae of Lorenzini to detect the electric fields produced by other animals; however, it was not known what extent the capsulated embryos were able to use this sense. Researchers from the University of Western Australia proposed that the encapsulated shark embryos are able use their electroreceptors to detect and protect themselves from predators.

In order to test their hypothesis, researchers introduced a predator-simulating electric field to encapsulated brownbanded bamboo shark embryos before and during the development of their electrosensory system. The embryos were able to detect predators in both stages; however, the fully developed embryos were able to detect predators that were 2.25 times further away than their younger siblings. Once detected, the embryos responded by ceasing all respiratory gill movement and body movement, thereby minimizing their electrosensory and mechanosensory outputs and avoiding detection.

So next time you are playing hide and seek, remember that you are not the only one who stays still to avoid detection!

Want to learn more about sharks? Visit our current seasonal feature, The Secret World of Sharks and Rays, on until April 7.


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